Problem: Simplify the following expression: $ p = -9 + \dfrac{-6x + 4}{9x} $
Explanation: In order to add expressions, they must have a common denominator. Multiply the first expression by $\dfrac{9x}{9x}$ $ \dfrac{-9}{1} \times \dfrac{9x}{9x} = \dfrac{-81x}{9x} $ Therefore $ p = \dfrac{-81x}{9x} + \dfrac{-6x + 4}{9x} $ Now the expressions have the same denominator we can simply add the numerators: $p = \dfrac{-81x - 6x + 4}{9x} $ $p = \dfrac{-87x + 4}{9x}$